Due to actualization of environmental problems in recent years, hybrid cars and electric cars have spread. Further, as an air conditioner device which is applicable to such a vehicle, there has been developed an air conditioner device which includes an electric compressor to compress and discharge a refrigerant, a radiator (a condenser) disposed in an air flow passage to let the refrigerant radiate heat, a heat absorber (an evaporator) disposed in the air flow passage to let the refrigerant absorb heat, and an outdoor heat exchanger disposed outside a vehicle interior to let the refrigerant radiate or absorb heat, and which changes and executes respective operation modes of a heating mode to let the refrigerant discharged from the compressor radiate heat in the radiator and let the refrigerant by which heat has been radiated in this radiator absorb heat in the outdoor heat exchanger, a dehumidifying and heating mode to let the refrigerant discharged from the compressor radiate heat in the radiator and let the refrigerant by which heat has been radiated absorb heat in the heat absorber and the outdoor heat exchanger, a dehumidifying and cooling mode to let the refrigerant discharged from the compressor radiate heat in the radiator and the outdoor heat exchanger and let the refrigerant by which heat has been radiated absorb heat in the heat absorber, a cooling mode to let the refrigerant discharged from the compressor radiate heat in the outdoor heat exchanger and let the refrigerant absorb heat in the heat absorber, and the like.
Furthermore, there is provided an air mix damper in the air flow passage, and with this air mix damper, a ratio at which air is to be passed through the radiator is adjusted in an entire range from zero, thereby achieving a target outlet temperature to the vehicle interior (e.g., see Patent Document 1).
To control the air mix damper in this case, as a parameter, an air volume ratio SW at which the air is to be passed through the radiator is used, and the ratio is obtained by a calculating equation of SW=(TAO−Te)/(TH−Te), in which TAO is a target outlet temperature, TH is a temperature of a radiator 4, and Te is a temperature of the heat absorber. In all operation modes, the air volume ratio SW changes in a range of 0≤SW≤1 in which 0 indicates an air mix shut off state where the air is not passed through the radiator, and 1 is an air mix fully open state to pass all the air in the air flow passage through the radiator.